Did someone open the display case?
Not to my recollection. VS Not to my knowledge.
Can both be said?
But they mean different things - as different as memory is to knowledge. And they would be used in different situations.
"Not to my recollection" implies that if the display case had been opened, the speaker would have been in a position to notice it.
I think you are making too fine a point here. A person might have been in a position to notice something but didn't see it or forgot that it happened. Knowing and remembering are not very far apart. If something happened in the past, we cannot know it if we don't remember it.
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